1. Field of the Invention
The present invention relates to a surface-mounting type electronic circuit unit.
2. Description of the Related Art
Generally, such a surface-mounting type electronic circuit unit is substantially formed so that various circuit components are soldered on each soldering land of a conductive pattern provided on a board and are covered with a shield. An end-face electrode is provided to the side of the board and when the electronic circuit unit is mounted on the surface of a mother board, the end-face electrode is soldered on a soldering land of the mother board. Circuit components are used according to required circuit configuration including a tuning circuit, a resonant circuit or an amplifying circuit, for circuit components for a resonant circuit for example, a diode, a chip capacitor and an inductor are used, for circuit components for an amplifying circuit, a transistor, a chip resistor, a chip capacitor and an inductor are used and these circuit components are connected via a conductive pattern.
Heretofore, an electronic circuit unit substantially formed as described above on which a unbalance/balance converter for transforming an unbalanced signal to a balanced signal and outputting it is mounted is known. Normally, this unbalance/balance converter is formed by a surface mounting component including a pair of conductors on a flat dielectric substrate, an unbalanced signal can be transformed to a balanced signal in the unbalance/balance converter by soldering an electrode provided on the dielectric substrate on a conductive pattern on a multilayer board and can be output.
Recently, technology for miniaturizing a circuit component such as a chip component and a semiconductor component has remarkably progressed and for example, microminiature chip resistor and chip capacitor the respective outside dimensions of which are approximately 0.6xc3x970.3 mm are also realized. Therefore, if such a microminiature circuit component is also used in the abovementioned conventional type electronic circuit unit and such circuit components are mounted on a board in a state in which pitch between the components is narrowed, the electronic circuit unit can be miniaturized to some extent. However, the miniaturization of a circuit component such as a chip component and a semiconductor component has a limit and in addition, as a part where each circuit component is soldered is required to be prevented from being short-circuited when multiple circuit components are mounted on aboard, the reduction of pitch between components also has a limit and these have greatly prevented the further miniaturization of an electronic circuit unit. Further, as a unbalance/balance converter is formed by a surface mounting component and the surface mounting component is relatively large-sized because a pair of conductors are arranged beside longer than predetermined length to secure a desired degree of coupling, limited mounting space on a board is narrowed by the surface mounting component for the unbalance/balance converter and the miniaturization of an electronic circuit unit is also prevented from this standpoint.
As a distributed inductor for resonance is formed by a microstrip line provided on a multilayer board in the abovementioned conventional type electronic circuit unit, the microstrip line required to acquire desired Q is extended and the miniaturization of the electronic circuit unit is also prevented from this standpoint.
The invention is made in view of the situation of such conventional type technique and the object is to provide a surface-mounting type electronic circuit unit suitable for miniaturization and also excellent in a countermeasure for static electricity.
To achieve the object, in the electronic circuit unit according to the invention, circuit elements including a capacitor and a resistor and a conductive pattern connected to these circuit elements are thinly formed on an alumina substrate, a semiconductor bare chip is mounted on the alumina substrate, the semiconductor bare chip is bonded to the conductive pattern via wire, an inductance element composed of a pair of conductors opposite at a predetermined interval on the alumina substrate is thinly formed and an unbalance/balance converter is formed by the inductance element.
According to such configuration, as circuit elements including the capacitor and the resistor are precisely formed using thin-film technology and in addition, a bare chip for a semiconductor device is bonded via wire, circuit components required on the alumina substrate are densely mounted and the surface-mounting type electronic circuit unit suitable for miniaturization can be realized. Further, as the inductance element composed of a pair of conductors is thinly formed on the alumina substrate and the unbalance/balance converter is formed by a pair of conductors of the inductance element, a gap between both conductors is reduced, a desired degree of coupling can be secured and the electronic circuit unit also has an advantage to miniaturization from this standpoint.
In the abovementioned configuration, when a pair of conductors forming the unbalance/balance converter are formed on the same surface of the alumina substrate, a gap between both conductors is reduced and the degree of coupling can be enhanced. Also, when a pair of conductors are laminated on the alumina substrate via the insulator, space for both conductors occupied on the alumina substrate can be more reduced. Further, it is desirable that a pair of conductors are formed in a spiral shape or zigzag.
Also, in the electronic circuit unit according to the invention, circuit elements including a capacitor, a resistor and an inductance element and a conductive pattern connected to these circuit elements are thinly formed on a square flat alumina substrate, a semiconductor bare chip bonded to the conductive pattern via wire is mounted, an electrode for input and an electrode for output respectively connected to the conductive pattern are provided on the side of the alumina substrate and a close part for discharge is provided to the conductive pattern connecting at least one of the electrode for input and the electrode for output and the capacitor.
According to such configuration, as circuit elements including the capacitor, the resistor and the inductance element are precisely formed using thin-film technology and in addition, the bare chip for the semiconductor device is bonded via wire, circuit components required on the alumina substrate are densely mounted and the surface-mounting type electronic circuit unit suitable for miniaturization can be realized. As the close part for discharge is provided to the conductive pattern connecting at least one of the electrode for input and the electrode for output and the capacitor though the resistance to voltage of the capacitor particularly out of circuit elements thinly formed on the alumina substrate is reduced, the breakdown of the capacitor by static electricity can be securely prevented and in addition, as the close part can be formed with high dimensional precision by thin-film technology, the gap for discharge in the close part is reduced and discharge at low voltage is enabled.
In the above-described configuration, the conductive patterns are opposite arranged on the alumina substrate, it is desirable that the projection is respectively opposite provided to these conductive patterns to form the close part and as a result, the breakdown of the capacitor by static electricity can be securely prevented.
Also, in the electronic circuit unit according to the invention, circuit elements including a capacitor, a resistor and an inductance element respectively thinly formed and a semiconductor bare chip bonded on an alumina substrate via wire are provided on the alumina substrate, the inductance element includes at least an inductance element for setting a resonance frequency and the inductance element for setting a resonance frequency is thinly formed in a spiral shape.
According to such configuration, as circuit elements including the capacitor, the resistor and the inductance element are precisely formed using thin-film technology and in addition, the bare chip for a semiconductor device is bonded via wire, circuit components required on the alumina substrate are densely mounted and the surface-mounting type electronic circuit unit suitable for miniaturization can be realized. Also, as a concentrated constant type inductor is formed by the inductance element for setting a resonance frequency in a spiral shape thinly formed, distance between the conductors is reduced, the inductance element can be miniaturized and the miniaturization of the electronic circuit unit can also be realized from this standpoint.
In the abovementioned configuration, it is desirable that Cu plating is provided on the surface of the inductance element in a spiral shape forming the inductance element for setting a resonance frequency and hereby, Q of a resonant circuit can be enhanced.
Also, in the abovementioned configuration, it is desirable that a conductive pattern for regulation connected to the inductance element for setting a resonance frequency is thinly formed and the number of turns of the inductance element for setting a resonance frequency is increased by trimming the conductive pattern for regulation to regulate a resonance frequency and hereby, a resonance frequency can be simply regulated. In this case, it is desirable that the conductor width of the trimmed conductive pattern for regulation and the conductor width of the inductance element f or setting a resonance frequency are substantially equalized and hereby, the characteristic impedance of both is equal.